Although fetal exposures during pregnancy have always been a concern of teratology research and reproductive epidemiology, less is known about toxic exposures before pregnancy that might impair fertility or about the effects of fetal exposures on subsequent infant and child health. We think that important insights may be gained by the epidemiologic study of occupational and environmental exposures during each of these stages in the development process. We have begun a research program to address how three groups of environmental toxicants, anesthetic gases, metals, and pesticides affect fertility, fetal development, and infant and childhood development.